Basement impact assessment in Barnet

Trees, gardens and Article 4 areas in Barnet

A basement under a garden stops tree roots as well as water. Barnet records 718 tree preservation orders and 3,219 protected zones, so a mature tree near a proposed excavation is the norm, not the exception. An arboricultural report usually travels with the assessment, and the engineer must show how the roots and the new walls coexist.

Planning control is also tighter in places than the national rules suggest. The borough has 15 Article 4 directions across 48 mapped areas, and 16 conservation areas. A direction can remove permitted development for the front of a house, so a lightwell visible from the street is a design decision that needs permission.

Historic England lists 651 entries in the borough, and 9 appear on the Heritage at Risk Register. Under a listed house, the heritage case sits next to the ground report.

What the appeal record tells a basement applicant

Barnet decided 1,361 householder applications in its latest year and granted 80.2 per cent, with 95.1 per cent decided in time.

The Planning Inspectorate decided 413 householder appeals against the borough, and allowed 50.6 per cent of them. That is a useful reminder that a refusal is not always the last word, but it is not a reason to submit a weak scheme. We prefer to resolve the council's concerns before you apply.

None of these figures is specific to basements, because the published statistics group all householder work together. They show how the borough treats ordinary schemes, and a basement is not ordinary: officers look for evidence rather than assurances, so the engineer's findings must be visible on the sheets the council reads.

Digging beside neighbours: party wall and building rules

With 52.5 per cent of households living in houses rather than flats, a basement here often runs close to a neighbour's flank wall. Under the Party Wall etc. Act, a notice is needed for excavation within 3 metres of an adjoining building if it goes deeper than that building's foundations, and within 6 metres on the diagonal test. Notice goes out at least 1 month before work.

The neighbour then has 14 days to answer in writing before a dispute is treated as having arisen. A calm, early conversation, with our sections attached, usually saves time here.

If the council asks for a flood or drainage statement, the Building Regulations floor test applies as well: drainage is needed where the water table can rise to within 0.25 metres of the lowest floor.

Price, route and nearby places

A basement impact assessment is an unpriced service. After the check we send a fixed quote, and the planning application that carries it is covered by our planning drawings in Barnet service.

For the wider borough picture, see architectural drawings in Barnet. Next door, Camden publishes a detailed five-stage process, which is a good guide to how specialists structure a report, and the national rules are on the basement impact assessment hub.